The present invention is directed to a vacuum-packaging machine, which continually forms packages from two layers of thin film conveyed to different stations by means of a conveyer, at which stations separate processes are performed. The packages formed may, or may not, be vacuum-packed. The typical vacuum-packaging machine has a first, forming station where a lower film is formed into a plurality of pockets, or main holding sections, of the plurality of packages being formed at any one time. From this first, forming station, the film is transferred to a second, loading station, where the actual product to be packaged is placed in the previously-formed pockets at the first station. After loading, the film is transferred, or indexed, to a third, sealing station, where an upper film is placed on top of the lower film, which has already been formed into pockets and loaded with product, which upper film is then sealed to the lower film, to thereby form a plurality of sealed vacuum-packages. Finally, the joined, sealed packages are conveyed to a fourth, cutting station, where the joined packages are cut into individual vacuum-packages for shipment and/or storage. The sealing station may be provided with two, separate, sealing sub-sections, as disclosed in U.S. Pat. No. 4,951,444, where an initial seal is followed by a final seal. It is at the forming station and the sealing station where the greatest amount of time is spent, since the film must come to a rest and await the completion of the respective process, before the conveyer can again index the film; thus, the productivity of the machine is limited by the amount of dwelling time spent at these two stations.
At each of the forming and sealing stations above-mentioned, there is a dedicated tool-head, which is lifted toward the film in order to perform either the forming or sealing process. After the specific task has been completed, the tool is then lowered, and then raised again after the conveyer has indexed another portion of the film to that station. As disclosed in U.S. Pat. No. 4,951,444, the raising of these tools is commenced prior to the time that the actual indexing of the film has been completed, i.e., while the conveyer is still transporting the film, before the section of the film to be processed next has completely reached and become stationary at the station, in order that a considerable amount of time be saved. The amount of time saved by such preactuation of the tools is considerable, resulting in marked increases in productivity.
The present invention is directed to further increases in the productivity of vacuum-packaging machines.